New evidence for the links between the local water cycle and the underground wet sand layer of a mega-dune in the Badain Jaran Desert, China

Abstract

Scientists and the local government have great concerns about the climate change and water resources in the Badain Jaran Desert of western China. A field study for the local water cycle of a lake-desert system was conducted near the Noertu Lake in the Badain Jaran Desert from 21 June to 26 August 2008. An underground wet sand layer was observed at a depth of 20-50 cm through analysis of datasets collected during the field experiment. Measurements unveiled that the near surface air humidity increased in the nighttime. The sensible and latent heat fluxes were equivalent at a site about 50 m away from the Noertu Lake during the daytime, with mean values of 134.4 and 105.9 W/m 2 respectively. The sensible heat flux was dominant at a site about 500 m away from the Noertu Lake, with a mean of 187.7 W/m 2 , and a mean latent heat flux of only 26.7 W/m 2. There were no apparent differences for the land surface energy budget at the two sites during the night time. The latent heat flux was always negative with a mean value of-12.7 W/m 2 , and the sensible heat flux was either positive or negative with a mean value of 5.10 W/m 2. A portion of the local precipitation was evaporated into the air and the top-layer of sand dried quickly after every rainfall event, while another portion seeped deep and was trapped by the underground wet sand layer, and supplied water for surface psammophyte growth. With an increase of air humidity and the occurrence of negative latent heat flux or water vapor condensation around the Noertu Lake during the nighttime, we postulated that the vapor was transported and condensed at the lakeward sand surface, and provided supplemental underground sand pore water. There were links between the local water cycle, underground wet sand layer, psammophyte growth and landscape evolution of the mega-dunes surrounding the lakes in the Badain Jaran Desert of western China.

Assimilation of Cosmic‐Ray Neutron Counts for the Estimation of Soil Ice Content on the Eastern Tibetan Plateau

“…While applying the theory by Philip and De Vries (), traditional coupled water and energy models that simulate states in the unsaturated zone widely disregard the flow of the gas phase (Zeng et al, ). Nevertheless, the gaseous phase (water vapor and dry air) flow mechanism has been shown to substantially enhance the vapor transport in arid regions (Wen et al, ; Zeng, ; Zeng, Su, et al, ; Zeng, Wan, et al, ; Zeng & Su, ). This has led to the development of multiphase models such as STEMMUS (Zeng et al, ).…”

New observational and experimental evidence for the recharge mechanism of the lake group in the Alxa Desert, north-central China

“…the desert lakes are mainly recharged by groundwater, and the local rainfall is not the major replenishment source of the groundwater and lakes. Wen et al (2014) observed the local water cycle near the Nuoertu Lake for three months with automatic weather station and eddy covariance system in the Badain Jaran Desert in 2008. Three rainfalls with the total precipitation of 50.0 mm occurred during 17 days, but the average volumetric sand moisture below 60 cm remained lower than 6% and had no variation throughout.…”

“…The few hydrometeorological observations (Gu et al, 2004;Wen et al, 2014) in the desert were only short term or discontinuous because of the extreme conditions, which has led to controversial interpretations.…”

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